We have previously proposed that whey might be fermented with yeasts which are capable of producing substantial amounts of fatty acids triglycerides (fat or oil). Moon, N. J. & Hammond, E. G., Abst. 202, J. Amer. Oil Chemists Soc., Feb., 1977, Vol. 54, No. 2, p. 156 A. Further, the lipid composition of a wide variety of yeasts has been studied and reported. Kaneko, et al, "Lipid Composition of 30 Species of Yeasts," Lipids 11: 837-844 (1976). Species of the genus Candida were referred to but not Candida curvata. See also Erwin, J. A., "Comparative Biochemistry of Fatty Acids in Eukaryotic Microorganisms," in Lipid and Biomembranes of Eukaryotic Microorganisms, J. A. Erwin, Ed., Academic Press, N. Y., pp. 114-117 (1973).
U.S. Pat. No. 3,818,109 of Robert M. Bechtle describes the conversion of whey solids to an edible yeast cell mass. A combination of bacteria and yeasts are employed for the fermentation, and it is indicated that the yeasts may include species of the genera Candida. Candida curvata is not mentioned, and there is no suggestion that the yeast cell mass would contain oil. In the Bechtle process, the medium is prepared from concentrated whey containing whey protein and lactose in the same proportions as in the usual whey obtained from cheese manufacturing operations.
Liquid whey resulting from cheese manufacturing operations is processed by ultrafiltration to prepare a whey protein concentrate. A by-product of such ultrafiltration is referred to as "whey permeate". It consists of the liquid and dissolved solids which pass through the ultrafiltration membranes. The permeate solids can be recovered, such as by condensation of the permeate liquid in an evaporator, and further treatment in a spray dryer to produce the permeate solids as a dry powdery material. Such permeate solids, however, have limited uses and their commercial value is relatively low compared to the whey protein concentrate which may contain 30% or more protein. The permeate solids are composed principally of lactose together with a minor amount of nitrogenous material (polypeptides, amino acids, etc.). Since whey protein concentrate is prepared on a large scale in the United States with the resulting whey permeate by-product, there has been a recognized need to find new uses for the permeate material, and/or to develop processes for modifying and improving the value of the permeate material.